The invention relates to connecting rods for two-cycle internal combustion engines.
In two-cycle internal combustion engines, the sidefaces of the connecting rods at their crank ends are typically silver plated to bear the frictional rubbing contact with the crankarms or discs of the crankshaft. The expense of silver plating is objectionable.
In the electroplating process, an initial pre-cleaning step is performed, followed by masking. Masking is an expensive process of painting the rods and then removing the mask in selected areas. An oil film must then be applied for corrosion control, and typically the parts are then shipped to an electroplating plant. The electroplaters then must the clean the rods again, and then silver plate. After plating, the rods must be baked immediately at about 350.degree. F. for four hours minimum to prevent hydrogen embrittlement. The rods must then be allowed to cool to ambient temperature, and returned to the manufacturing plant. The rods then must be vibrated in a steel media to remove the meniscus edge which has been built up. The rods must then be inspected for thickness and adhesion of the silver plating.
In the present invention, the rods are cleaned, and then a polymeric coating having a low coefficient of sliding friction is applied, followed by curing for about 30 minutes, and an inspection for thickness. The rods are then passed on to the next operation. The invention solves prior problems of poor adhesion of the mask or silver plating. The invention eliminates: one of the prior cleaning processes; prior corrosion control problems; prior shipping requirements; the prior baking requirement for preventing hydrogen embrittlement; the prior vibration operation; the flow of parts back and forth from the shipping dock and to an electroplating plant. The invention also eliminates or reduces work in process and improves line flow. The invention thus significantly reduces production cost.
The invention also reduces the coefficient of friction to prevent galling, premature wear, friction welding, and heat generation by the two rotating and/or sliding members. The coating can be applied by a spray, brush, silk screen, etc.